Fate of 2 Year-Old, Hatchery-Reared Trout Cod Maccullochella Macquariensis (Percichthyidae) Stocked Into Two Upland Rivers
Journal of Fish Biology (2007) 71, 182–199 doi:10.1111/j.1095-8649.2007.01481.x, available online at http://www.blackwell-synergy.com Fate of 2 year-old, hatchery-reared trout cod Maccullochella macquariensis (Percichthyidae) stocked into two upland rivers B. C. EBNER*†‡, J. D. THIEM*† AND M. LINTERMANS*† *Parks, Conservation & Lands, Department of Territory & Municipal Services, ACT Government, G. P. O. Box 158, Canberra ACT 2601, Australia and †Cooperative Research Centre for Freshwater Ecology, University of Canberra, ACT 2601, Australia (Received 16 June 2006, Accepted 13 February 2007) Radio-tracking was used in monitoring the reintroduction of on-grown 2 year-old trout cod Maccullochella macquariensis (Percichthyidae) (a nationally endangered freshwater fish) in both a large and small upland river. Thirty-six radio-tagged M. macquariensis were stocked into a site in each of the Murrumbidgee and Cotter Rivers (Australian Capital Territory). Restricted dispersal occurred in both rivers, with both samples of M. macquariensis remaining within 5 km of the release site for the duration of the study. Mortality was rapid and 1 month after release 61 and 31% of the sample was alive in the Murrumbidgee and Cotter Rivers, respectively. In the Murrumbidgee River, complete mortality had occurred 6 months after release. An individual survived in the Cotter River until 7 months after release. Predation by cormorants Phalacrocorax spp. and predation or scavenging by the common water rat Hydromys chrysogaster were the probable causes of mortality. Predator-assisted movement of radio-tags by cormorants occurred in both groups and had the potential to confound interpretation of active dispersal movements.
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